I´m trying to create that personalized style for hidrography representation (in blue at the Picture); the lines must have 0.2 mm of edge, 3 mm of length, the space between lines must be 1.5 mm and the points, with 0.4 mm of size, must be between in the center of all between-lines spaces. Anybody could teach me how to build that style?
This style has two components: a dashed-line and a marker on top of it.
You start by creating a simple line, and you select a custom dash pattern. Make sure it is in millimeters. You set 3 dash and 1.5 space. Set the width and color.
Then, using the Plus sign, you add a second marker line. You select it as a point, set the width and color. The tricky part is to locate it properly: the middle of the space are 3+1.5 mm away from each other, so your point should be placed every 4.5mm. Since you don't want it at the beginning of the dash line but in the middle of the space, you need to offset the location by 3 + 1.5/2 = 3.75 mm